Table Of ContentMaterials and Reliability Handbook for
Semiconductor Optical and Electron Devices
Osamu Ueda (cid:129) Stephen J. Pearton
Editors
Materials and Reliability
Handbook for Semiconductor
Optical and Electron Devices
Editors
OsamuUeda StephenJ.Pearton
GraduateSchoolofEngineering UniversityofFlorida
KanazawaInstituteofTechnology Gainesville,FL32611,USA
Tokyo,Japan
ISBN978-1-4614-4336-0 ISBN978-1-4614-4337-7(eBook)
DOI10.1007/978-1-4614-4337-7
SpringerNewYorkHeidelbergDordrechtLondon
LibraryofCongressControlNumber:2012947361
#SpringerScience+BusinessMediaNewYork2013
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Preface
Thishandbookcoversreliabilityproceduresandapproachesformodernelectronic
andphotonicdevices,includinglasersandhigh-speedelectronicsusedinallaspects
ofourlives,fromcellphonestosatellites,datatransmissionsystems,anddisplays.
Reliability offers significant experimental and modeling challenges. Typically,
parts cannot betested until they fail under normal operatingconditions.Since the
target is frequently a decade or longer of useful life, this is impractical. Conse-
quently, accelerated testing is performed. This procedure only works when the
physicsiswellunderstood,andthefailuremechanismisnotacceleratedbyfactors
notunderthecontrolofthetesting.Modelingofthefailuremechanismiscrucialin
making extrapolated predictions of lifetime. Computer-Aided Design tools have
advancedtothepointwheremultiplefactorsinfluencingreliabilitycanbeincluded
intestingsimulations.
Lifetime prediction for compound semiconductor device operation is notori-
ously inaccurate due to the fragmented efforts in reliability and the absence of
standardprotocols.Engineershaveusuallyreliedonacceleratedtestingatelevated
temperaturewithextrapolationbacktoroom-temperatureoperation.Thistechnique
frequentlyfailsforscaled,high-current-densitydevices.Devicefailureisdrivenby
electric field or current mechanisms or low activation energy processes that are
masked by other mechanisms at high temperature. Device degradation can be
drivenbyfailureineitheractivestructuresorpassivationlayers.
In this handbook, we have attempted to provide comprehensive coverage of
reliabilityengineeringforIII-Vdevicestructures,includingmaterialsandelectrical
characterization, reliability testing, and electronic characterization. These latter
techniques are used to develop new simulation technologies for device operation
and reliability. In turn, these techniques allow accurate prediction not only
of reliability but also the ability to design structures specifically for improved
reliability of operation. While the characterization and accelerated testing and
diagnostics isolate the factors controlling reliability, the simulation capability
based on the characterization results can help to predict and better explain device
reliability.Therefore,thereisextensivefeedbackbetweentheseapproaches.
v
vi Preface
ThebasicunitoffailureinSidevicetechnologyistheFIT(failureunit),defined
as 1 failure/109 device hours. For 100 devices on test, a failure rate of 1,000 FIT
would mean there would be only 1 failure in 1 year. Given that a relatively
small number of devices will actually show failure, it is critical to both enhance
the failure rate through accelerated testing (the five common stresses used are
temperature, voltage, current, humidity, and temperature cycling) and treat the
resultingreliabilitydatacorrectly.Inanystudyunderacceleratedagingconditions,
different failure mechanisms may be accelerated by different amounts for the
sameappliedstress.Acceleratedagingisusefulonlyifweknowthefailuremecha-
nism. In Si MOS devices, time-dependent failure mechanisms include surface
chargeaccumulationorinjection,dielectricbreakdown,electromigration,andcon-
tactdegradationandcorrosionduetocontamination.Incompoundsemiconductors,
we have the added issues of local regions of nonstoichiometry that affect field
distributions and increase recombination, oxidation of AlGaAs or AlGaN, high
densities of dislocations, and other extended defects in some structures and high
surfacestatedensities.
WealsocoverstandardSireliabilityapproachestodeterminetheinstantaneous
failure rate and mean time to failure and therefore the distribution functions most
relevanttothespecificdevicetechnology.ItisexpectedthattheWeibulldistribu-
tionisthemostrelevant,sincethefailureratewilllikelyvaryassomepowerofthe
ageofthedevice.Inthiscase,thefailurerate,l(t),isgivenby
lðtÞ¼ðb=aÞtb(cid:2)1
whereaandbareconstants.Forb > 1,thefailurerateincreaseswithtime,which
is likely for compound devices, as defect migration or creation and oxidation
orcontactdegradationoccur.Intheearlypartofreliabilitystudies,Duaneplotting
is also relevant to allow a quick prediction of failure rates when the number of
devicefailuresislow.Inthisapproach,thelogoftheaveragefailurerate(fraction
of failed devices at time t divided by the time) is plotted as a function of the log
of time. The log-normal distribution function is a more general approach for
describing the failure statistics over wide spans of time. It may also be the case
thattherewillbetwoormorefailurepopulationsduetothepresenceofmorethan
one failure mechanism. This can be resolved on a log-normal distribution that
revealsthedifferenttimedependenceofthevariousfailuremechanisms.
This handbook focuses attention on voltage and current acceleration
stress mechanisms. Many studies in Si indicate that the reaction rate of the
failure mechanism is proportional to a power of the applied voltage as well as
temperature,i.e.,
RðT;VÞ¼ROðTÞVgðTÞ
where the coefficient RO(T) is an Arrhenius function of T and the power depen-
dence varies between 1 and 4.5. This determines how much acceleration occurs
with increases in the bias voltage during stressing. If dielectric breakdown is the
Preface vii
dominantfailuremode,thenatagivenfield,afractionofthedeviceswillfailina
shorttime,withnoadditionalfailuresuntilanincreasedfieldisapplied.
Part1ofthisbookcoversopticaldevicessuchaslight-emittingdiodes(LEDs)
and laser diodes (LDs) including conventional edge-emitting lasers (or edge
emitters) and vertical-cavity surface-emitting lasers (VCSELs). Since the earliest
stages in the history of R&D of III-V optical devices (mid-1960s), long-term
reliability has been one of the key issues. This part of the book provides overall
featuresoflifetestingofoptical devicesandresultsforvarious changes indevice
characteristics corresponding to a variety of device degradation modes or root
causes. In order to clarify the physical phenomena occurring in the degraded
regions, one must do various failure analyses on the degraded devices. In this
part, detailed modern failure analyses for optical devices are systematically
presented.
Concerning the degradation, three major failure (degradation) mechanisms are
distinguished as follows: classical rapid degradation due to “dark-line defects
(DLDs)formation”andrecombination-enhanceddislocationmotion,gradualdeg-
radationduetorecombination-enhancedpointdefectreactionwhichdeterminesan
ultimatelifetimeofthediodes,andcatastrophicfailure(catastrophic optical dam-
age(COD)incaseofedgeemitters).Otherdegradationmodessuchasdegradation
due to ESD/EOS, acceleration of gradual degradation due to local lattice strain,
degradationpeculiartohigh-powerlaseroperation,etc.,arealsodescribed.Itisalso
worthyofnotethatthebookfocusesindetailonmaterialsissuesanddegradationof
InGaN/GaN LDs. The VCSEL chapter is also informative for those working on
reliabilitystudiesaswellastheR&DofVCSELchipsand/orcomponentsinwhich
VCSELs are used as key devices. Fundamental physics buried in the degradation
phenomena,i.e.,theoryonrecombination-enhanceddislocationglide(REDG)and
recombination-enhanceddefectreactions(REDR),aresystematicallyreviewedby
professionalsinthisparticularfield.
Thesecondpartofthebookfocusesonelectricaldevicessuchasheterojunction
bipolartransistors(HBTs)andhighelectronmobilitytransistors(HEMTs).Thereis
tremendouscurrentinterestindeterminingthedegradationandfailuremechanisms
of short gate length high electron mobility transistors in the AlGaN/GaN and
AlGaAs/GaAs systems under athermal, voltage, or current-driven conditions and
innewmethodologiestopredictandmitigateagainstdevicefailureunderpractical
operating conditions. The failure mechanisms have typically involved factors
such as metal contact reaction with the semiconductor or insulation on a local
scale near the high-field regions between the gate anddrain, ora new mechanism
called the inverse piezoelectric effect in which high biasing leads to lattice
distortions and eventually formation of cracks that can then be oxidized or filled
with metal by migration from the contacts. The presence of such failure
mechanisms means that local probes for determining compositional and bonding
changes on a local scale near the contacts are needed. Ultimately, the need is to
determinethemechanismsfortheobservedincreasesindevicecurrentatthreshold
valuesofelectricfield,andthenprovidethatinformationtoasimulationcodeused
forpredictingfailure.
viii Preface
In sum, this book is the first to cover all aspects of compound semiconductor
devicereliability.Researchresultsonreliabilityandmaterialsissuesofbothoptical
and electrical devices since 2000 are systematically described. Readers will find
characterizationtechniquesneededtounderstandfailuremechanismsincompound
semiconductor devices, the statistics and experimental approaches to reliability
studies, and finally case studies of laser degradation and HEMT degradation
amongthekeybenefits.
Tokyo,Japan OsamuUeda
Gainesville,FL,USA StevePearton
Acknowledgements
TheeditorswishtothankSaraKateHeukerottandDavidPackerofSpringerUSfor
guidingthisprojecttocompletion.MuchoftheworkatUFwassupportedinpartby
anAirForceOfficeofScientificResearchMultiDisciplinaryUniversityResearch
InitiativemonitoredbyJimHwang.
Prof.OsamuUeda,KanazawaInstituteofTechnology,Japan
Prof.StevePearton,UniversityofFlorida,Gainesville,FL32611,USA
ix
